A note about before and after at NSIDC

Some readers may have noticed the sharp uptick at NSIDC for the Southern Hemisphere sea ice extent, as highlighted in WUWT Sea Ice News #13:

Here is how it looks today at NSIDC:

Source: http://nsidc.org/data/seaice_index/images/daily_images/S_timeseries.png

So that there aren’t any speculations about the sudden disappearance of data, I’ve asked Walt Meier of NSIDC about it and posted the response:

Hi Walt,

Do you have any idea why the southern sea ice extent uptick disappeared?

Before, July 10

http://climateinsiders.files.wordpress.com/2010/07/s_timeseries1.png

After, July 11

http://nsidc.org/data/seaice_index/images/daily_images/S_timeseries.png

No mention of it anywhere

http://nsidc.org/arcticseaicenews/

Seems rather odd to make such a correction and not notify end users of such  a change. This lack of notice then leads to speculative phrases, like “death  spirals”. 😉

Best Regards,

Anthony Watts

He answered within minutes. Walt is very good about being responsive on issues related to NSIDC. For that he should be commended.

Hi Anthony,

It was an error in the source data we use in the sea ice algorithm we  run. We have an automated QC that will take it out, but it requires data  from the following day. We can QC manually too, but since it happened on  a Sunday no one was around to address it. It did get corrected  automatically when processing occurred this morning.

We generally don’t post a notice for isolated incidents like this since  it is just a part of routinely dealing with near-real-time data. We do a  general discussion on our FAQ:

http://nsidc.org/arcticseaicenews/faq.html#quality_control

Thanks.

walt

I may have more from Walt in the coming day or two. Stay tuned.